The Football Association says more than 2,000 of its 28,000 referees - from the grassroots to elite level - come from a black or minority ethnic (BAME) background.

But Mannix believes there is a lack of visible black officials - and a lack of role models inspiring others to pick up the whistle.

If you went to most BAME referees and asked them who is the highest profile black referee working in the game, they wouldn't know

"Everyone wants to play like Messi, everyone wants to play like Ronaldo, they can idolise and they can see it," said Mannix. "But if you can't see anyone, how can you idolise it? We've got one National League black referee.

"Until you see someone, you can't relate to them. I'm sure if you went to most BAME referees and asked them who is the highest-profile black referee working in the game, they wouldn't know."

Ironically, it was precisely the lack of black officials that convinced Mannix to get involved. "I remember when Uriah Rennie left in 2009, and I remember looking and thinking 'who else is there?' There's no-one, and I'm thinking 'I can do that'," he said.

Yet he does not expect others to do the same until football authorities get tougher on racism.

And Mannix, who runs his own security company and has acted as a bodyguard for world heavyweight boxing champion Anthony Joshua, UFC fighter Conor McGregor, singer Selena Gomez and television celebrities the Kardashians, says football needs to increase diversity among coaches, managers and the media too.

He said football was being held back "massively" by racism and a lack of diversity - "and there are no punishments for it".

Mannix has acted as a bodyguard for reality star Kim Kardashian and UFC fighter Conor McGregor

"Last week we had someone that came on the pitch and punched somebody, and they got jailed for 14 weeks - the correct punishment. But if you get someone who shouts out racial abuse, they get their season ticket taken away," added Mannix.

"Someone in the hierarchy has got to say 'no we're not having it, and take 10 points away from teams' - but then you'll have every legal person saying 'that's not fair'.

"Say someone racially abuses a player, throws a banana, gets banned, but then can potentially still come back in on a friend's season ticket. You're never going to stop it - it's part of the game.

"Until it changes from the top, people aren't going to change."

Clubs and police do act on fan behaviour, with recent examples including a Tottenham fan banned from football for four years and fined after throwing a banana skin during the north London derby, and four Chelsea fans suspended after Manchester City's Raheem Sterling was allegedly racially abused at Stamford Bridge.

A banana skin was thrown at Arsenal striker Pierre-Emerick Aubameyang during the Gunners' home game against Tottenham in December

"Those with power do not exercise their responsibilities in the way that will help us deal with this problem," Lord Ouseley said.

That came after Premier League bosses met with the 20 top-flight chairmen "to encourage more people from different backgrounds to take up coaching, refereeing and administrative roles in the sport".

Sports minister Mims Davies has also called on football leaders to try to tackle racism and discrimination in the sport.

The FA last year launched its 'In Pursuit of Progress' inclusion plan, to make football "better reflect modern society".

Mannix says he has not suffered abuse personally, but has heard it from crowds.

He has progressed to the FA's Centre of Refereeing Excellence but missed out on a promotion last year to referee in the National League, and said he has felt "an undercurrent" of racist attitudes in the game.

Mannix feels a support network for ethnic minority referees is needed to help encourage more BAME officials.

An FA spokesman told BBC Sport: "The FA recognises the value of a diverse group of referees and we continue to offer support and development opportunities for referees from all backgrounds and across all levels of the game.

"The face of refereeing is continually changing and becoming a better representation of the football community.

"We continue to see a rise in the number of women and BAME referees in English football and we encourage people of all backgrounds to join the refereeing community."